Self-tapping drain plug or bolt



S p 1941- E. L. WYLIE 2,257,441

SELF-TAPPING DRAIN PLUG OR BOLT .Filed Jan. 4, 1941 F/6.1 F/6.Z

ATTORNEY Patented Sept. 30, 1941 SELF-TAPPING DRAIN PLUG OR BOLT ErnestL. Wylie, St. Louis, Mo., assignor to Champ-Items Inc., St. Louis, Mo.,a corporation of Missouri Application January 4, 1941, Serial No.373,106 1 Claim (01. 85-47) When this occurs'a costly labor jobresults,-

because it is almost impossible to use the next larger tap, either S. A.E. or U. S. S., owing to the fact that in many instances the amount ofmetal in the crankcase is insuflicient to permit the use of an oversizedtap. Furthermore it is not considered practical to put an ordinarymachine screw without a gasket in the oil pan or crankcase and expect tomake a satisfactory repair.

The principal object of my invention is to provide an oversized drainplug which is so constructed that it will cut its own threads as it isinserted in the aperture from which the threads have been stripped.

A further object of my invention is to so construct the plug that it canbe removed after the thread has been cut and the chips removed when theplug itself which has been used as a tap can then be re-inserted andused as a drain plug, a special gasket being furnished for this p pose.

A further object of my invention is to so construct the plug that theheel of'each portion of the'plug which cuts the threads will besumciently low to free the chips resulting from the threading operation.

My means of accomplishing the foregoing obf iects maybe more readilyunderstood by having reference to the accompanying drawing which is outaxial displacement.

Similar reference numerals refer to similar parts throughout the entirespecification.

As shown in the drawing, I form my improved drain plug from bar stock ona regular screw machine (not shown).

After the plug has been cut oif it is placed in a milling machine andtwotransverse slots 2 and 3 are milled in the threaded portion 4 of plug I.These slots 2 and 3 are at right angles to each other and pass throughthe axis ofthe plug I as clearly shown in Fig. 1 and Fig. 2. It has beenfound in practice best to make these slots to extend approximately onehalf the length of the plug.

After the slots are milled the plug is placed in a punch press and aspecial cam ground conical punch is employed to swage the four ends 5,i, I, and 8, upwardly as illustrated in Fig. 4. An examination of thisFig. 4 of the drawing will show that the heel 9 of each of the four endsis lower than the cutting edge ID of the threads. The plug is thenhardened and tempered and is then ready to be used for the purposeintended.

By compressing the ends of the plug after it has been threaded thecutting edges or points iii are caused to bite the metal firmly whencutting the new thread, thereby insuring a perfect thread in thecrankcase or oil pan. The plug is provided with the usual hexagonal headll, al-

though obviously the shape of the head is largely a matter of choiceprovided it is so shaped that a tool can be employed to tighten it.

I have found in practice that it is desirable to have a plain orunthreaded portion I2 adjacent the head II, on which to mount a gasketit.

Having described my invention what I regard as new and desire to secureby Letters Patent is:

A self-tapping drain plug comprising a head, a unidirectional-portiontapered laterally, said portion being threaded for tapping and havingtwo transverse slots'intersecting along the axis of the plug therein setat thereby forming four segmented portions. said segmentedportions eachbeing swaged inwardly along one of its plane faces thereby exposing fourcutting edges with- ERNES'I L. WYLIE.

